Known in the art is a method for preparing polymers and copolymers of higher .alpha.-olefines comprising polymerization or copolymerization of the starting monomers such as vinylcyclohexane, 4-methylpentene-1, hexene-1, in the presence of a heterogeneous catalyst which is soluble neither in the monomer medium nor in the reaction medium, containing an organoaluminium compound such as triethylaluminium, diethylaluminium chloride and titanium chlorides employed in the ratio of 1:1 and above. The polymerization is conducted in an organic solvent medium such as heptane, hexane, or in the medium of a liquid monomer at a temperature within the range of from 50.degree. to 100.degree. C. under a gauge pressure.
An obligatory condition of the polymerization resides in elimination of the possibility of penetration, into the reactor wherein the process is conducted, of other foreign substances active in respect of organometallic compounds, such as water oxygen, etc. As a result of the polymerization a suspension of the polymer in the solvent is usually formed. In such method the stage of polymerization is followed by the stage of separation and purification of the resulting solid polymer. Separation of the polymer is effected by separation of the solvent (or the monomer in excess) by way of filtration, centrifugation or distillation. Purification of the resulting polymer from the remaining amounts of the catalyst is effected by way of decomposition of the latter at an elevated temperature 100.degree. C. in an alcohol which has been previously added into the suspension of the polymer in a hydrocarbon solvent, whereafter the polymer is washed with the same alcohol (usually twice) and then centrifuged. It is also possible to remove the catalyst by washing with water simultaneously with the treatment of the resulting polymer with a live steam at a temperature of 100.degree. to 105.degree. C. Such removal of the catalyst is generally performed in different apparatus, followed by separation of water by centrifuguation. The thus-produced solid polymer is then dried.
However, the use of alcohol added into the polymer suspension for decomposition of the catalyst complicates the technology of regeneration of the solvent or liquid monomer.
An embodiment of the catalyst removal from the suspension of the resulting polymer by treating said suspension with live steam results in the formation of substantial amounts of waste waters which, owing to the presence of hydrochloric acid, are aggressive, and therefore special measures are required against equipment corrosion.
A principal disadvantage of the prior art method resides in relatively low rates of polymerization and conversion of monomers. Thus, conversion of vinylcyclohexane after 6 hours is usually below 40%, while conversion of 4-methylpentene-1 for the same period is 50-60%. In case of using heterogeneous catalysts based on titanium chlorides, stereoregulation is ensured by the regular crystalline surface of titanium chloride and by the influence of a number of atoms disposed on the crystalline surface, on the process of stereoregular growth of the polymer chain.
Furthermore, as it has been already mentioned hereinabove, the prior art method features a complicated procedure of decomposition of a heterogeneous catalyst and removal of its residues from the reaction mass.
Also known in the art is a method for preparing polyethylene and copolymers of ethylene with another monomer such as propylene by way of contacting said monomers with a homogeneous catalyst (soluble in a carbon medium) based on alkyl aluminium chloride compounds such as a dialkylaluminium chloride and organic derivatives of vanadium such as trialkylvanadate at the ratio between the alkylaluminium chloride compound and vanadium compound of at least 3:1, in a medium of a hydrocarbon solvent. The polymerization is effected at a temperature within the range of from 0.degree. to 70.degree. C. and under an elevated pressure (of up to several dozens of atmospheres).
After the completion of such polymerization process no special treatment of the resulting polymer is required for the decomposition of the catalyst residues.
The production of polyethylene or copolymers of ethylene with the use of homogeneous catalytic systems offers technological advantages of the homogeneous catalysts possessing a high catalytic activity and enabling isolation of the resulting polymers without any troubles inherent in the methods contemplating the use of heterogeneous catalysts.
However, the prior art homogeneous catalysts are suitable only for the production of polyethylene or copolymers of ethylene with another monomer, for example propylene.
It has been thought that a solid crystalline surface of a catalyst is necessary for the formation of stereoregular crystalline higher polyolefines. In some papers it has been pointed out that homogeneous catalyst do not substantially enable polymerization of higher .alpha.-olefines and contribute to the formation of low-molecular non-crystalline polymers (cf. W. L. Carreck et al. J. Am. Chem. Soc. 1960, 82, No. 15, pp. 3883-3892; J. Henrici-Olive and S. Olive J. Polymer. Sci. 1970, B, No. 2, p. 205-210).
Known is the process for the preparation, with the use of homogeneous catalysts, of so called syndiotactic polymers such as polypropylene (cf. A. Lambell et al. Macroprol. Chem. 1968, 112, pp. 160-183), but this process is of no practical importance due to an extremely low rate of polymerization and necessity of carrying out the reaction at a low temperature (below -10.degree. C.).
It may be noted that inefficiency of homogeneous catalytic systems such as dialkylaluminium chloridetetraalkoxytitanium or dialkylaluminium chloride-trialkyl vanadate in the production of stereoregular crystalline polymers of higher .alpha.-olefines is associated, on the one hand, with chemical instability of the catalytic complexes formed in such systems (the occurence of rapid reversible and irreversible chemical reactions of transformations of the complexes) and, on the other hand, with an insufficient stereoregulating ability of the formed complexes, i.e. their ability to coordinate the propagating end of the polymer chain connecting the monomer in a strictly specific stereo-manner so as to produce a specific stereo configuration of the polymer chain.
In the case of using the known homogeneous catalytic systems, the resulting catalytic complex is substantially a point active center containing no sufficient amount of atoms or ions capable, as it has been mentioned hereinbefore, of ensuring a strict coordination of the growing polymeric chain and the monomer. Therefore, only for the production of polymers and copolymers of ethylene such two-component homogeneous catalytic systems are effective due to the fact that a molecule of ethylene is symmetric, it has no large-size substituents at the double bond, wherefore a high stereo-regulating ability of the catalyst is not necessary for polymerization of ethylene with the formation of a regularly arranged polymer chain.
It is an object of the present invention to overcome the above-mentioned disadvantages.
It is an object of the present invention to provide such a simplified method for the production of polymers and copolymers of higher .alpha.-olefines, wherein the polymerization would occur at a higher rate of the formation polymers and copolymers and a higher rate of conversion as well.
This object is accomplished by that in the preparation of polymers and copolymers of higher .alpha.-olefines polymerization of copolymerization of the starting monomers is effected in the presence of a catalyst containing an alkylaluminium chloride compound and a compound a transition metal belonging to Group IV of the Periodic Table, in a hydrocarbon medium, followed by separation of the solvent and the remaining catalyst from the resulting polymer or copolymer, in accordance with the present invention, said polymerization or copolymerization is effected in the presence of a catalyst additionally containing a trialkylvanadate, while as the compound of a transition metal use is made of an alkoxyderivative of titanium or zirconium, or hafnium.
Owing to the method according to the present invention it is now possible to substantially increase the rate of polymerization and conversion in the preparation of polymers and copolymers of higher .alpha.-olefines. Thus, in the preparation, by the prior art method, of a polymer from 3-methylpentene-1 only 60% of the monomer are converted to the polymer for 20 hours, whereas the method according to the present invention makes it possible to reach a conversion rate as high as 70% even after 4 hours of polymerization. In the production of a polymer from vinylcyclohexane by the prior art method less than 30% of the monomer are converted to polymer over 4 hours, whereas the method according to the present invention makes it possible to convert, within the same time period, already 90% of the starting monomer. Polymers of higher .alpha.-olefines produced by the method according to the present invention have a stereoregular structure with a high degree of crystallinity, which is manifested in an increased melting point of the resulting polymers; thus the resulting polyvinylcyclohexane has its melting point above 350.degree. C., poly-3-methylpentene-1 has its melting point above 320.degree. C., poly-4-methylpentene-1 has its melting point above 230.degree. C.
To maximally increase the rate of polymerization and the rate of conversion, in accordance with the present invention it is advisable that the catalyst would contain an alkylaluminium chloride compound, chloride compound, an alkoxy derivative of titanium or zirconium or hafnium, and a trialkylvanadate at the following molar ratios between said components: 5.0-100:0.2-5:1 respectively.